In a skillet, saute scallions and garlic in oil. Add mushrooms and olives or beans and cook over medium heat for 2 to 3 minutes.
Squeeze out liquid from spinach with your hands. Add spinach and salt to skillet. Saute briefly.
Pour enchilada sauce into a wide bowl. Place two 8- or 9-inch pie plates next to bowl. Dip 8 tortillas in the sauce, coating both sides. Lay 4 tortillas on the bottom of each pie plate, overlapping as necessary.
Divide the sauteed mixture between the pans, covering tortillas. Sprinkle 1/2 cup of cheese over filling in each pan. Dip remaining 8 tortillas and overlap them on top of cheese. Spread any remaining sauce over tortillas; top with remaining cheese.
Bake pies at 350° F. for 35 to 40 minutes.